Experimental evaluation of effective surface energy for cleavage microcrack propagation across grain boundary in steels
Experimental evaluation of effective surface energy for cleavage microcrack propagation across grain boundary in steels
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DOI：
10.1016/j.actamat.2018.02.057
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发表时间：
2018-05
期刊：
影响因子：
9.4
通讯作者：
Itsuki Kawata;H. Nakai;S. Aihara
中科院分区：
文献类型：
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作者：
Itsuki Kawata;H. Nakai;S. Aihara
进行断裂试验和有限元分析，以评估与穿过钢晶界的微裂纹扩展相对应的有效表面能 γ mm 的温度依赖性。为了能够评价γmm，准备了含有粗大渗碳体粒子的钢。由于渗碳体颗粒较大，在这些钢中，微裂纹穿过晶界扩展的临界断裂应力被认为大于微裂纹穿过渗碳体颗粒和铁素体晶粒之间界面扩展的临界断裂应力；因此，通过有限元分析估计的局部断裂应力和通过断口分析获得的断裂起始位置反映了微裂纹穿过晶界扩展的临界断裂应力。因此，通过使用为本研究制备的钢，可以观察到根据局部断裂应力计算出的 γ mm 的精度得到了提高。此外，使用含有不同镍浓度的钢研究了镍对γmm的影响。 γ mm 值的评估考虑了相邻小面相对于裂纹萌生小面的方向和混合模式应力强度因子。作者提出了 γ mm 的新温度依赖性。此外，观察到镍添加对 γ mm 的影响可以忽略不计。本研究的结果可以有效地用于开发基于微观结构信息的概率解理断裂模型。
Fracture tests and finite element analysis were conducted to evaluate the temperature dependence of the effective surface energy γ mm corresponding to microcrack propagation across the grain boundary of steels. Steels containing coarse cementite particles were prepared to enable γ mm evaluation. The critical fracture stress of microcrack propagation across the grain boundary is considered larger than the critical fracture stress of microcrack propagation across the interface between a cementite particle and a ferrite grain in these steels because of the large cementite particles; therefore, local fracture stress estimated by finite element analysis and fracture initiation site obtained by fractography reflect the critical fracture stress of microcrack propagation across the grain boundary. Thus, the accuracy of γ mm calculated from local fracture stress is observed to be enhanced by employing the steels prepared for the present study. In addition, the effect of nickel on γ mm was studied using steels containing different concentrations of nickel. Values of γ mm were evaluated considering both the direction of a neighboring facet relative to the crack initiation facet and the mixed mode stress intensity factors. The authors proposed a new temperature dependence of γ mm. Additionally, the negligible effect of nickel addition on γ mm was observed. The results of the present study can be used effectively to develop a probabilistic cleavage fracture model based on microstructural information.